1. Field of the Invention
This invention relates to a pyroelectric IR-sensor (infrared sensor), and more particularly to a pyroelectric IR-sensor which have excellent characteristics and is easy in manufacturing.
2. Description of the Prior Art
A conventional pyroelectric IR-sensor essentially comprises a pyroelectric light receiving element, a substrate or base plate of alumina for supporting the pyroelectric light receiving element in a manner that this pyroelectric light receiving element is spaced from the substrate by spacing pads, and provided with a wiring pattern and a resistor formed on the surface thereof, and an FET chip mounted on the substrate.
The method of manufacturing the above-mentioned pyroelectric IR-sensor will be described hereinafter.
At first, a substrate is provided by forming a wiring pattern and a resistor by silk screen printing and baking on an alumina plate molded in a predetermined shape. Next, a FET chip is soldered onto the substrate. Then, a conductive paste is put on the substrate, the top of the paste and suitably the paste is flattened hardened to provide spacing pads. Finally, a pyroelectric light receiving element is bonded on the spacing pads.
Since the pyroelectric light receiving element serves to sense changes in temperature in response to infrared rays, this element must be thermally isolated from other components.
To realize this, in the above-mentioned conventional pyroelectric IR-sensor, the pyroelectric light receiving element is spaced from the substrate by the spacing pads and is thus thermally isolated therefrom.
Since heat is transferred through the spacing pads, however, the thermal isolation is insufficient. Further, since it is extremely difficult to form the spacing pads with a high precision, unevenness occurs in the thermal isolation of the pyroelectric light receiving element. This causes unevenness in the characteristics if the pyroelectric light receiving elements. Furthermore, occurs an unbalance in transfer of heat through the spacing pads which support the pyroelectric light receiving element. This causes the production of noises by an unbalanced voltage.
In addition, it takes a relatively long time in the process for forming the spacing pads. This constitutes obstacle to an improvement in productivity.